Camino Acner, Zang Pengxiao, Athwal Arman, Ni Shuibin, Jia Yali, Huang David, Jian Yifan
Casey Eye Institute, Oregon Health & Science University, Portland, OR 27239, USA.
Department of Engineering Science, Simon Fraser University, Burnaby, Canada.
Biomed Opt Express. 2020 Jun 24;11(7):3952-3967. doi: 10.1364/BOE.396829. eCollection 2020 Jul 1.
Optical coherence tomographic angiography (OCTA) can image the retinal blood flow but visualization of the capillary caliber is limited by the low lateral resolution. Adaptive optics (AO) can be used to compensate ocular aberrations when using high numerical aperture (NA), and thus improve image resolution. However, previously reported AO-OCTA instruments were large and complex, and have a small sub-millimeter field of view (FOV) that hinders the extraction of biomarkers with clinical relevance. In this manuscript, we developed a sensorless AO-OCTA prototype with an intermediate numerical aperture to produce depth-resolved angiograms with high resolution and signal-to-noise ratio over a 2 × 2 mm FOV, with a focal spot diameter of 6 µm, which is about 3 times finer than typical commercial OCT systems. We believe these parameters may represent a better tradeoff between resolution and FOV compared to large-NA AO systems, since the spot size matches better that of capillaries. The prototype corrects defocus, astigmatism, and coma using a figure of merit based on the mean reflectance projection of a slab defined with real-time segmentation of retinal layers. AO correction with the ability to optimize focusing in arbitrary retinal depths - particularly the plexuses in the inner retina - could be achieved in 1.35 seconds. The AO-OCTA images showed greater flow signal, signal-to-noise ratio, and finer capillary caliber compared to commercial OCTA. Projection artifacts were also reduced in the intermediate and deep capillary plexuses. The instrument reported here improves OCTA image quality without excessive sacrifice in FOV and device complexity, and thus may have potential for clinical translation.
光学相干断层扫描血管造影(OCTA)能够对视网膜血流进行成像,但由于横向分辨率较低,毛细血管管径的可视化受到限制。自适应光学(AO)可在使用高数值孔径(NA)时用于补偿眼部像差,从而提高图像分辨率。然而,先前报道的AO - OCTA仪器体积庞大且复杂,并且视野(FOV)小于1平方毫米,这阻碍了具有临床相关性的生物标志物的提取。在本论文中,我们开发了一种具有中等数值孔径的无传感器AO - OCTA原型,以在2×2毫米的视野内产生具有高分辨率和信噪比的深度分辨血管造影图,焦斑直径为6微米,比典型的商用OCT系统精细约3倍。我们认为,与大数值孔径AO系统相比,这些参数可能在分辨率和视野之间实现了更好的权衡,因为光斑尺寸与毛细血管的光斑尺寸更匹配。该原型基于视网膜层实时分割定义的平板的平均反射投影,使用品质因数来校正散焦、散光和彗差。能够在任意视网膜深度(特别是视网膜内层的神经丛)优化聚焦的AO校正可在1.35秒内完成。与商用OCTA相比,AO - OCTA图像显示出更强的血流信号、信噪比和更细的毛细血管管径。在中间和深层毛细血管丛中,投影伪像也减少了。本文报道的仪器在不过度牺牲视野和设备复杂性的情况下提高了OCTA图像质量,因此可能具有临床转化潜力。